Magnesium base alloy



FFlCE UNITED STATES PAT MAGNESIUM BASE ALLOY Joseph D. Hanawalt and John O. McDonald, Midland, Mich., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Michigan No Drawing. Application November 13, 1939,

Serial No. 304,125 7 3 Claims. (Cl. 75-168) The invention relates to magnesium base alto .6 per cent of silver, 0.1 to 0.3 per cent ofcalloys. It more particularly concerns alloys of this c u 1 to 3 p ce t o a a e 2 to per nature having a high degree of formability coucent of zinc, and from 4 to '7 per cent of tin. pled with other improved physical properties, Alloys containing the higher percentages oi al- 5 such as increased tensile and yield strengths. S/ g ingredients, While Still having good ductil' '5 Magnesium alloys are enjoying increasing use i y have p i n ly high yield and tensile in the structural and mechanical arts where a properties and thus are also, suitable forfluse in light weight metal is highly desirable, such as casting op r for use in making large castings, forgings, and The specific proportions of each alloying the like. However, the use of these alloys in the metal and the total amount of the added metals 1o rolled form to make sheet metal articles requirto be employed in these new alloys depends on ing forming operations, such as bending, drawthe use for which the alloy is intended. In ing, and the like, has not progressed as rapidly general it is preferable to use alloys containing due to the fact that in general alloys of good more than about 82 per cent magnesium and less formability permitting relatively sharp bends to than 18 per cent of the total added metals. For 15 be made without the article developing external example, in alloys wherein high ductility or formcracks usually have inferior characteristics as ability is of prime importance, the total added regards their tensile and yield strengths. alloying metals should not materially exceed 10 It is, accordingly, the principal object of the per cent; while in those instances where high 30 invention to provide a magnesium base alloy yield and tensile strengths are desirable in both 0 which may be made into rolled sheet or the like, the cold rolled and annealed state, the percentpossessing a sufficient degree of ductility or age of total added metals should preferably be formability to be sharply bent, drawn or otherabove 12 per cent. wise shaped while having improved tensil and The following table, which lists some of the yield strengths. properties of rolled sheet metal made from our Other objects and advantages will be apparnew alloy and compares these properties with ent as the description of the invention proceeds. those of a related alloy, illustrates the improve- Our invention resides in the discovery that a ment" in yield strength, tensile strength, and magnesium base alloy composed of 0.3 to 8 per ductility or formability, as represented by the cent of silver, 0.05 to 1 per cent of calcium, 0.1 per cent increase in elongation of the new alloy v to Bper cent of manganese, 0.1 to 8 per cent of over the corresponding properties of closely rezinc, and from 0.1 to 8 per cent of tin, the bal- .lated alloy.

Table 35 ZtlfitiiiittttttfV we 001d rolled Yield Tensile Percent Yield Tensile Percent Ag. Ce. Mn. Sn. Zn. strength strength elongation strengthstrength elongation 40 4 in lbs./sq. in. inlbs./sq. in. in 2 inches inlbsJsq. in. in lbs./sq. in. 1n 2 inches 1.2 0.3 0.3 5.1 22,000 35,000 7 31,000 38 000 2 1.2 0.3 1.0 5.3 1.3 30,000 12 3a, 000 I 8 1.1 0.2 1.1 5.1 as 23,000 30,000 15 40,000 ,0 3

. 4s ance being substantially all magnesium, is en- The properties listed in the above table under dowed with the afore-mentioned properties. the section headed by the term annealed were While the properties of improved formability or obtained by first rolling the alloys at a temductility coupled with increased tensile and yield perature between about 500 to 700 F., an

59 strengths are manifest over the entire range of thereafter annealing them at various temperacomposition indicated, we have found that in tures through a temperature range of from 400 general the preferred-combination of properties, to 800 F. The properties selected for the table such as the most desirable, ductility for forming were those of the annealed specimens which exoperations coupled with high tensile and yield hibited the maximum elongation. The properstrengths is found in alloys containing from 1 ties listed under the section headed cold rolled 55 were obtained by subjecting specimens of the alloys which had been hot rolled at a temperature of from 500 to 700 F. to additional rolling in the cold state to bring about a total reduction in thickness of from 2 to 10 per cent. The properties selected for the table were those of the cold rolled specimens which showed the greatest tensile and yield strengths, while having at least a 1 per cent elongation in 2 inches.

By a comparison of the properties listed in the above table, it will be observed that the combined properties of our new polynary alloys are superior to those of the parent quintary alloys having similar percentages of alloying ingredients. For example, it will be noted that the per cent elongation is greatly improved while the yield and tensile strength in both the annealed and cold rolled state also show marked improvement. Similarly alloy compositions containing other percentages of the alloying ingredients show improved properties over those of the related alloys.

While the new alloy is most useful in wrought form, such as sheets, due to its formabiiity characteristics, it may also be suitably used in making castings, forgings, extruded forms, and the like. It is further pointed out that our new alloy is amenable to solution and precipitation heat treatments, which, accordingly, modify its properties.

The new alloy may be compounded in any ways known to the art, such as by adding the alloying ingredients to the molten magnesium under a suitable flux. The flux should be substantially free from magnesium chloride, if the calcium content of the alloy is to be above 0.3 per cent. In those instances where an alloy is to be compounded containing less than 0.3 per cent of calcium, magnesium chloride may be preseni in the flux without exerting a deleterious effect, but in this case it is usually desirable to add the calcium last and without too much stirring in order that the loss of calcium into the flux will be substantially prevented.

We claim:

1. A magnesium base alloy containing from 0.3 to 8 per cent of silver, 0.05 to 1 per cent of calcium, 0.1 to 3 per cent of manganese, 0.1 to 8 per cent of zinc, and from 0.1 to 8 per cent of tin, the balance being magnesium.

2. A magnesium base alloy containing from 1 to 6 per cent of silver, from 0.1 to 0.3 per cent of calcium, 1 to 3 per cent of manganese, 2 to 5 per cent of zinc, and from 4 to 7 per cent of tin, the balance being magnesium.

3. A magnesium base alloy containing from 6 to 8 per cent of silver, 0.3 to 0.7 per cent of calcium, 1 to 3 per cent of manganese, 6 to 8 per cent of zinc, and from 7 to 8 per cent of tin, the balance being magnesium.

JOSEPH D. HANAWALT. 'JoHN c. MCDONALD. 

